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• Cannot open videos in Opencv

  12 mai 2013, par Mahesh

  I am trying to open .avi file in opencv. When I run the code I do not get any error but the video does not play. I searched around and I guess it requires ffmpeg to be installed. So I installed it using
  sudo apt-get install libavformat-dev libavcodec-dev libavfilter-dev libswscale-dev
  It still does not work. Maybe the compiler needs to know where to find ffmpeg. I am using gcc compiler.
  Thanks.

  @Paul R : I have just copied the code from the Learning Opencv textbook, so wasn't including it. The code :

  #include
  
  #include
  
  int main( int argc, char** argv ) {
  
  cvNamedWindow( "Example2", CV_WINDOW_AUTOSIZE );
  
  CvCapture* capture = cvCreateFileCapture( argv[1] );
  
  IplImage* frame;
  
  while(1) {
  
      printf("Inside");
  
      frame = cvQueryFrame( capture );
  
      if( !frame ) break;
  
      cvShowImage( "Example2", frame );
  
      char c = cvWaitKey(33);
  
      if( c == 27 ) break;
  
  }
  
  cvReleaseCapture( &capture );
  
  cvDestroyWindow( "Example2" );

  }

  @praks411 :

  printf("%s",argv[1]);
  
  CvCapture* capture = cvCreateFileCapture( argv[1] );
  
  if(!capture)
  
  {   
  
          printf("failed\n");
  
      return -1; 
  
  }

  It prints the argument correctly and the capture fails.

• avconv : report the error for codec open failure

  20 juin 2013, par Luca Barbato

  avconv : report the error for codec open failure
  External codec may have corner case reason to fail at init, better
  
  report them instead having the user wonder.
  

  • [DH] avconv.c

• Ubuntu 16.04 + OpenCV + FFMPEG + CUDA don't open default camera

  20 juillet 2018, par Newton Pasqualini Filho

  I am trying to work with accelerated OpenCV using my own build of FFMPEG with CUDA support for GPU video processing using Python.

  My application must support any kind of video devices, including USB and IP cameras.

  I have a config file parsed with ConfigParser that loads the camera device path, as described in OpenCV documentation we can access usb camera by index number and for IP camera we use RTSP protocol so the path could be sometimes 0 or rtsp://192.168.1.2/0.

  To force the use of FFMPEG behind OpenCV I am trying to open the video capture stream like bellow :

  video_capture = cv.VideoCapture()
  
  stream_opened = video_capture.open(camera_path, cv.CAP_FFMPEG)

  The problem is when I try to open the default USB camera camera_path = 0 the video_capture.open method always returns false, but when it is a RTSP like camera_path = "rtsp://192.168.1.2/1" it open the video capture stream ok.

  When I let OpenCV decide what backend will be used it calls to GStreammer and it opens the capture stream like this :

  video_capture = cv.VideoCapture(camera_path)

  I suspect that FFMPEG does not have any support for capture video from a USB camera, does it ? Is there some missing feature to my ffmpeg build ?

  ffmpeg version N-91487-g1809f1c Copyright (c) 2000-2018 the FFmpeg developers
  
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10) 20160609
  
  configuration: --prefix=/usr --pkg-config-flags=--static --enable-cuda-sdk --enable-cuvid --enable-libnpp --extra-cflags=-I/usr/local/cuda/include/ --extra-ldflags=-L/usr/local/cuda/lib64/ --nvccflags='-gencode arch=compute_61,code=sm_61 -O2' --enable-gpl --enable-libass --enable-libfdk-aac --enable-libx264 --extra-libs=-lpthread --enable-libx265 --enable-nvenc --enable-nonfree
  
  libavutil      56. 18.102 / 56. 18.102
  
  libavcodec     58. 21.105 / 58. 21.105
  
  libavformat    58. 17.101 / 58. 17.101
  
  libavdevice    58.  4.101 / 58.  4.101
  
  libavfilter     7. 26.100 /  7. 26.100
  
  libswscale      5.  2.100 /  5.  2.100
  
  libswresample   3.  2.100 /  3.  2.100
  
  libpostproc    55.  2.100 / 55.  2.100
  
  Hyper fast Audio and Video encoder
  
  usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...